Automatic transmission



May 30, 1944.

J. BUCHHART 2,349,937

AUTOMATIC TRANSMISSION 0 Filed July 19, 1939 2 Sheets-Sheet 1 I "Lil-J:

May 30, 1944. J. BUCHHART AUTOMATIC TRANSMISSION Filed July 19, 1939 2 Sheets-Sheet 2 INAXENTOR BYQQZQL Q ATTORNEY-5 modified arrangement of the vehicle, but obviously is not limited to use in Patented May 30, 1944 .UNITED STATES PATENT OFFICE AUTOMATIC TRANSMISSION 1939, Serial No. 285,330 y July 22, 1938 Application July is, In German 8 Claims.

This invention relates to an automatic transmission, and more particularly to an arrangement for automatically shifting a speed-change gear in rwponse to the reaction torque developed in an-intermediate torque converter.

An object of this invention is to provide a novel, simple automatic transmission system.

Another object of this invention is the provision of an automatic transmission system wherein means are provided for automatically I of hydro-kinetic torque converter and speedchange drive, wherein the speed changes are produced automatically in response to the torque V on the reaction member of the torque converter.

Further objects and advantages of this invention will be apparent from consideration of the specification as illustrated bythe accompanying drawings of possible-embodiments of the invention in which drawings:

Fig. 1 is a schematic drawing of a preferred form of a complete power plant arranged in accordance with this invention:

Fig. 2 is an enlarged view of the automatic vtransmission control device diagrammatically portrayed in Fig. l;

Fig. 3 is a diagram illustrating the characteristics and operation of the transmission system;

Fig. 4 is a partially diagrammatic view of a system illustrated in Fig. 1, and

Fig. 5 is an enlarged view illustrating certain gtais oi the modified system portrayed in A preferred form of this invention is schematically illustrated in Fig. 1 which shows a prime engine, drivably connected to a torque converter I of the hydro-kinetic type having an impeller I, a turbine 4 and a reaction member 6, and thence to a speed-change drive generally indicated at 6. This power system is particularly adapted for use with a vehicle, such as a motor or railway this connection alone.

mover I. which may be an internal combustion The reaction member 5 of the hydro-kinetic torque converter 2 is preferably provided with an extended crank arm "i which cooperates with a' control device 8 for the control of the automatic speed-change 6.

A conduit 9 leading to the transmission control device 8 for a purpose hereinafter described is connected to the pressure side D of a pump. here shown as a gear pump l0, drivably connected through the worm i I with the impeller 3. A throttle I2 is preferably provided between the pressure side D of the pump Ill and the sump, while a conduit it supplies fluid to the pressure sides of the pump ill.

The speed or the internal combustion engine serving as the prime mover-l is adapted to be controlled by a throttling vane ll in the fuel supply, which is interconnected through link rod l5, crank it and link rod l'i with the usual foot pedal l8. Additional control of the throttling vane I4 is also eflected by the Bowden wire control device It connected to the Opposite end of the crank it from the link rod ii for a purpose to be hereinafter described. The wire is leads to the control device 8 (shown more fully in vFig. 2) which is also interconnected with the transmission by means of the control cable .20. While the transmission 6 may be of any well known remote controlled type, it is preferably electrically controlled in a manner well known. to the art and the connecting cable 20 may then contain the control wires for the electric transmission control device.

Referring more particularly to Fig. 2, the construction and operation of the control device 8 interconnecting the reaction member of the torque'converter for control of the automatic speed-change drive 6 will now be described with more particularity. In order to resist and oppose the torque on the reaction wheel 5, the crank arm I connected thereto is preferably movable between two piston drives 2l and 22 which include movable pistons 28 and 24 respectively, having respective hollow pressure spaces 25 and 2G to which a fluid under pressure is supplied from the pump I 0 through conduit 9. The pistons 23 and to the far end of the crank i and at its other end to a two-armed lever 33 shown as pivotally movable about a point 32. A second link rod 34 pivotally'connected at the other end of the two armed lever 33 actuates a double pawl and ratchet mechanism actuating a rotatable mem-.

ber 35 upon which is resiliently mounted a switch contacting arm 36. Through this arrangement,

movement of the cranklever I in one direction or the other will move the contact arm 36 from one contact 31 to another contact which will then electrically actuate the various changes in the transmission 6, in a manner well known to the'art.

The switch arm 36 is also preferably provided at its opposite end with, a notched section 38 against which one end of a. pivoted two-armed lever 39 is sprung, the other end of this lever being attached to the 'wire i9, connected as above described with the throttling vane 14 of the ensine i. The notches are so correlated with the contact 31 that while the switch arm 36 rests upon a contact, the wire I! will be in a normal position which. does not aflect the position of the throttling vane' l4. However, intermediate the contact 31 the notched section 38 will raise the 7 end of the lever 33 pressing against it to move the wire I! in such a direction that through the crank i6 and the link rod i5 the throttling vane I4 will be moved to its idling position. Thus, during the switching step, Dower is'removedfrom the torque converter which not only assures a quick assess? while at the same time in will remain substantially constant. Fig. 3 has been plotted to show the variations of M2 with increasing n: or both in]! throttle of the driving motor (solid lines) and partial throttle of the same (dash lines). The efliciency of the torque converter 2 is at its maxi mum when the transmission ratio is approximately 1: 1. This eiiiciency varies during increas- I ing speed 122 of the turbine element 4 as has been positive switching movement, but additionally permits the use of any type of clutching means in the. automatic transmission, such as a directdriving or dog clutch.

It .is to be noted that the pivot 32' for the linkee system interconnecting the crank arm with the switch for the automatic transmission 6 is h mounted upon a hand lever 40, pivoted at 4| and held in place by temporary stops 42, so that in.

this case the'pivot 32' is fixed. If it is desired to remove the control of the automatic transmis sion fromthe crank arm, the hand lever 40 may be disengaged from the temporary steps 42 by swinging them into the position indicated in dash lines, whereupon the pivot point 32 may be moved.

as desired by the lever 40 and thereby move the switch arm 36 in either direction at will. This arrangement is of particular importance when I it is desired to use the engine as a brake, in which case the transmission may be moved through the hand lever to a lower driving step. By restoring the hand lever 10 and the pivot point 32 to their original positions, automatic control of the transmission is instantly reinstated. g

. By reference to Figs. 1, 2 nd.3. the opera io of the above-described system will now be set forth. In order to clarify the'sequential operation, the various torques and forces arising have been given particular designations. The torque of the impeller 3 may be designated as M1, while the speed of this member has been designated as m.

Except during starting and during the time the engine is idling through control of the throttling vane l4, both Mi and m remain substantially constant. The torque and speed of the turbine member have been correspondingly respectively designated as M: and 122. Fig. 3 illustrates the manner in which M: will vary with increasing n:

indicated in Fig. 3, wherein such efficiency is designated as 11.

During initial starting of the engine the torque M; of the impeller 3 will be relatively small, that upon the stationary turbine element 4 (M2) very large, and the torque upon the reaction member 5 which may be designated as Mn will be correspondingly large, resolving itself into a force Ma as shown in Fig. 2. This force Ma will be so large, and the opposing reaction force Ma so small due to the low pressure resulting from slow speed 121 of the impeller 3, that the crank arm will move toward the right, as seen in Fig. 2 to hold the switch arm 36 in the lowest driving; connection. As the engine comes up to speed 111 will soon reach a constant value as'will the imingthis period nz will be increasing while Mr, as

seen in Fig. 3 will decrease. Shortly a point will be reached at which M: will be less than Mr which will then result in a torque on the reaction member 5 acting in the opposite direction and indicated in Figs. 2 and 3 as Mr}; As 11: increases to provide a slight overdrive, Mr. will have increased. to such a degree as to overcome the reaction force Ms and moves the crank arm I to the left.

As shown in Fig. 3, this may occur at the turbine rotor speed 712 As soon as the switch arm 36 moves to the next higher step and the transmission 6 is placed in-a higher gear, the torque M: will greatly increase over its previous value, and, to be sure, to such an extent that the torque upon the reaction wheel 5 may reverse and produce a force against the abutment indicated by Ma This reversed force will not, however, be suflicient to overcome the opposing force of the abutment Ms and the crank arm I will accordingly not move sufllciently to the right to cause a reversed action of the switch. mechanism. After the transmission has moved to the higher step, the speed of the turbine wheel 4 will be approximately nz as indicated in Fig. 3. This speed will then gradually increase again and switchin to additional higher speed will occur in substantially the same manner as described above for switching from the first to crank arm 1 to the right against the reaction force Ma 'to move the link rod 34 to the left, as seen in Fig. 2, thus switching the transmission from a higher to a lower gear. This change in transmission ratio will immediately decrease the torque M2 while the speed of the turbine member 4 will increase to m and produce a reverse force Mr." acting against the reaction force Ms Mr. is, however, less than Ms and the crank arm Y operate to reduce the drive mover, but also is true for partial loading.

cannot therefore continue moving to the left to again actuate the transmission to a higher step to nullify the previous reduction.

If the previously described reduction in transmission ratio is not sumcient the apparatus will has been reached.

In all cases between steps, due to the action of the notched sector 38 moving thewire it, the engine speed will be reduced. This removes the additional pressure from the pistons 23 and 24 and thus assures a quick positive movement of the crank arm providing, in turn, a quick positive movement of the switch arm 36. In this manner oscillation and hunting" or the crank arm I are -avoided.

It is to be particularly noted in connection with the operating curves illustrated in Fig. 3 that the maximum eiiiclency of the converter will occur approximately when the turbine element 4 has a speed 11:". The apparatus isso designed, how-. ever, that the range of speed covered by each transmission step are such that the eiiflciency never falls below 1 1, which is not far from mm. This is true not only for full throttle of the prime As a further importantmodiiication oi the con-' struction described above, it is possible that other means than the pump and pressure-operated pistons may be used to supply the reaction force opposing movement of the crank arm I attached to the reaction member 5. such an alternate arrangement has been illustrated in Figs. 4 and 5, where a generator I i suitably-geared to impeller 3 may supply current proportionate to the speed of the impeller through conductors III and H3 to electromagnet windings I25 and 128' which control respective armatures I23 and I24. The stationary members III and I22 serve in this case as guides ior'the armatures and asabutment for springs l2] and I28 pressing against the armatures I23 and I24 respectively. In this case the control device as a whole and as so modified has been designated as I'll. It isobvious that the operation of th system illustrated in Figs. 4 and 5 will produce proportionately the same results as that illustrated in Figs. 1 and 2.

While the principles of this invention are particularly applicable to the transmission of power for an automotive vehicle, it is obvious that its use may be extended to other vehicles, such as, for example, to the driving of railway vehicles, tractors, ships, elevators, etc. The exact type of prime mover is without importance. Furthermore, it is contemplated that other types of torque converters than the hydro-kinetic torque converter illustrated may be used. For example, an

hydraulic converter of the displacement type could be utilized. as could be mechanical and electrical torque converters. In all cases, however, in accordance with the principles of ,th s

until the lowest step necting said prime mover with said change-speed drive, said converter having a driver element connected to said prime mover, a driven element connected to said change-speed drive, and a reaction member, control means responsive to the torque on said reaction member for actuating said change-speed drive to change the speed to a higher ratio upon a decrease in the torque load of the driven element below a predetermined minimum, and to change the speed to a lower ratio upon an increase in the torque load of the driven element above a predetermined maximum, said control means being ineffective to cause a change in said change-speed drive at that torque on the reaction member corresponding to the maximum transmission eiiiciency of said converter, and means for disabling said control means from actuation by said reaction member and permitting control of said change-speed drive at will.

2. In combination, a prime mover, a changespeed drive having a plurality oi predetermined driving ratios, a hydraulic torque converter drivably connecting said prime mover with said change-speed, drive, said converter having a driver element connected to said prime mover, a driven element connected to said change-speed drive, and a reaction member having a crank arm, control means actuated by said crank arm for changing the ratio of said change-speed drive, a pump coupled with said driver element, pistons abutting on opposite sides of said'crank arm, and conduits leading from said pump to said piston for supplying pressure opposing movement of said crank arm.

3. The combination according to claim 2, in which said torque converter is hydro-kinetically operated, said driver element is an impeller, and said driven element is a turbine.

4. In combination, a prime mover, a changespeed drive having a plurality of predetermined driving, ratios, a hydraulic torque converter drivably connecting said prime mover with said change-speed drive, said converter having a driver element connected to said prime mover, a driven element connected to said change-speed drive, and a reaction member having a crank arm, control means actuated by said crank arm for changing the ratio of said change-speed drive, a gen erator coupled with said driver element, and elecinvention, the automatictransmission would be controlled by the torque produced upon tion member.

It will therefore be understood that this invention is not intended to be limited to the forms specifically described and illustrated, but is capabie of many further modifications within the knowledge of those skilled in the art without departing from the invention as defined by a proper interpretation of theiollowing claims.

I claim:

1'. In combination, a prime mover, a change speed drive having a plurality of predetermined the reacdriving ratios, a torque converter drivably conerator and mounted on opposite sides of said crank arm to oppose movement thereof.-

5. In combination, a prime mover, a step-bystep change-speed drive, hydro-kinetic torque converter drivably connecting said prime mover with said change-speed drive, said converter having an impeller connected to said prime mover, a turbine element connected to said change-speed drive, and a reactionmember having an extending crank arm, a pair of movable abutments on opposite sides of said crank arm, springs for pressing said abutment against said crank arm,

'means responsive to the speed of said impeller for supplementing the force of said spring, a control arm for changing the ratio of said changespeed drive, a double pawl and ratchets for moving said control arm in opposit directions, and

linkage means interconnecting said double pawl for actuation by said crank arm.

6.,The combination according to claim 5, in which said speed-responsive means includes a pump coupled to said impeller, a pair of hollow movable pistons abutting against said crank arm,

a source of fluid, and conduits for supplying said aeeaeev 8. The combination according to claim 5, in

combination with speed-control means for said prime mover including an idling position, and means responsive to movement of said control 5 arm between changes of said change=speed drive for moving said position.

speed-control means ivo'said idling 

